U.S. patent number 10,001,441 [Application Number 14/866,835] was granted by the patent office on 2018-06-19 for modification processing device, modification monitoring device and modification processing method.
This patent grant is currently assigned to OSAKA UNIVERSITY, SCREEN HOLDINGS CO., LTD.. The grantee listed for this patent is OSAKA UNIVERSITY, SCREEN Holdings Co., Ltd.. Invention is credited to Akira Ito, Iwao Kawayama, Hidetoshi Nakanishi, Yuji Sakai, Masayoshi Tonouchi.
United States Patent |
10,001,441 |
Nakanishi , et al. |
June 19, 2018 |
Modification processing device, modification monitoring device and
modification processing method
Abstract
There is provided a technique for easily inspecting the
modification state of a film in a semiconductor substrate. A
modification processing device modifies a film by irradiating a
semiconductor substrate with pulsed light emitted from a light
irradiation part. The modification processing device includes an
electromagnetic wave detection part for detecting an
electromagnetic wave pulse including a millimeter wave or a
terahertz wave radiated from the semiconductor substrate in
response to the irradiation with the pulsed light. The modification
processing device further includes a modification determination
part for determining the modification state, based on the intensity
of the electromagnetic wave pulse.
Inventors: |
Nakanishi; Hidetoshi (Kyoto,
JP), Ito; Akira (Kyoto, JP), Kawayama;
Iwao (Suita, JP), Tonouchi; Masayoshi (Suita,
JP), Sakai; Yuji (Suita, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
SCREEN Holdings Co., Ltd.
OSAKA UNIVERSITY |
Kyoto
Osaka |
N/A
N/A |
JP
JP |
|
|
Assignee: |
SCREEN HOLDINGS CO., LTD.
(Kyoto, JP)
OSAKA UNIVERSITY (Osaka, JP)
|
Family
ID: |
55585262 |
Appl.
No.: |
14/866,835 |
Filed: |
September 25, 2015 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20160093539 A1 |
Mar 31, 2016 |
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Foreign Application Priority Data
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|
|
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Sep 26, 2014 [JP] |
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2014-196295 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01J
1/42 (20130101); H01L 21/26 (20130101); G01N
21/6489 (20130101); H01L 22/12 (20130101); G01N
21/3586 (20130101); H01L 22/20 (20130101); H01L
21/268 (20130101) |
Current International
Class: |
G01J
5/02 (20060101); G01N 21/64 (20060101); H01L
21/26 (20060101); G01J 1/42 (20060101); H01L
21/66 (20060101); G01N 21/3586 (20140101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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H01-239863 |
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Sep 1989 |
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JP |
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H05-094959 |
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Apr 1993 |
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JP |
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2006-147848 |
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Jun 2006 |
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JP |
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2008-004694 |
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Jan 2008 |
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JP |
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2009-175127 |
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Aug 2009 |
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JP |
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2011-014914 |
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Jan 2011 |
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JP |
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2013-019861 |
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Jan 2013 |
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JP |
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Z013-072843 |
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Apr 2013 |
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JP |
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2013-170864 |
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Sep 2013 |
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JP |
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2014-078660 |
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May 2014 |
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JP |
|
Other References
Office Action issued in corresponding Japanese Patent Application
No. 2014-196295, dated Dec. 12, 2017 (w/partial English
translation). cited by applicant.
|
Primary Examiner: Malkowski; Kenneth J
Attorney, Agent or Firm: McDermott Will & Emery LLP
Claims
What is claimed is:
1. A modification processing device for modifying a film by
irradiating a semiconductor substrate with light, comprising: a
light irradiation part for irradiating a semiconductor substrate
with light for modifying said film; an electromagnetic wave
detection part for detecting the intensity of an electromagnetic
wave including a millimeter wave or a terahertz wave radiated from
said semiconductor substrate in response to the irradiation with
light for modifying said film; a modification determination part
for determining the modification state of said film of said
semiconductor substrate, based on changes generated due to
modification of said film proceeded by the irradiation with said
light in the intensity of said electromagnetic wave detected by
said electromagnetic wave detection part; and an irradiation
control part for controlling the irradiation with light for
modifying said film of said semiconductor substrate, based on a
result of determination of said modification determination
part.
2. The modification processing device according to claim 1, further
comprising a PL light detection part for detecting photoluminescent
light radiated from a surface of said semiconductor substrate by
the irradiation with light from said light irradiation part,
wherein said modification determination part determines the
modification of said semiconductor substrate, based on the
intensity of the electromagnetic wave detected by said
electromagnetic wave detection part and said photoluminescent light
detected by said PL light detection part.
3. The modification processing device according to claim 1, wherein
the light emitted from said light irradiation part is pulsed light
which modifies the film of said semiconductor substrate and which
generates an electromagnetic wave in said semiconductor
substrate.
4. The modification processing device according to claim 1, wherein
when said modification determination part determines that the
modification of said film of a region irradiated with said light is
completed, said light irradiation part stops the irradiation with
said light.
5. A modification processing method of modifying a film by
irradiating a semiconductor substrate with light, comprising the
steps of: (a) irradiating a semiconductor substrate with light for
modifying a film; (b) detecting the intensity of an electromagnetic
wave including a millimeter wave or a terahertz wave radiated from
said semiconductor substrate in response to the irradiation with
light for modifying said film in said step (a); (c) determining the
modification state of said film of said semiconductor substrate,
based on changes generated due to modification of said film
proceeded by the irradiation with said light in the intensity of
said electromagnetic wave detected in said step (b); and (d)
controlling the irradiation with light for modifying said film of
said semiconductor substrate, based on a result of determination in
said step (c).
6. The modification processing method according to claim 5, wherein
when said step (c) determines that the modification of said film of
a region irradiated with said light is completed, the irradiation
with said light in said step (a) is stopped.
7. A non-transitory, computer-readable medium encoded with
executable instructions that, when executed by one or more
processors, cause a modification processing device to perform
operations comprising: irradiating, for a first period of time, a
first area of a film of a semiconductor substrate with light for
modifying the film of the semiconductor substrate; detecting a
first intensity of an electromagnetic wave at a first time within
the first period of time and a second intensity of the
electromagnetic wave at a second time within the first period of
time, wherein the electromagnetic wave is generated from radiation
of the light from the first area of the film of the semiconductor
substrate during the first period of time; determining a
modification state of the film of the semiconductor substrate based
on changes between the first intensity and the second intensity of
the detected electromagnetic wave during the first period of time;
and adjusting the irradiation with the light for modifying the film
of the semiconductor substrate according to a result of the
determination of the modification state of the film of the
semiconductor substrate.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a process for modifying a film of
a semiconductor substrate and, more particularly, to a technique
for inspecting a modification state.
Description of the Background Art
During a manufacture of a semiconductor device, a film quality
process for modifying the quality of a film of a semiconductor
substrate by irradiating a surface of the semiconductor substrate
with light has been performed (for example, as disclosed in
Japanese Patent Application Laid-Open No. 2011-014914, Japanese
Patent Application Laid-Open No. 2008-004694 and Japanese Patent
Application Laid-Open No. 2014-078660).
Japanese Patent Application Laid-Open No. 2011-014914 discloses the
technique of irradiating a silicon substrate with a pulsed laser
having a pulse width of 10 to 1000 femtoseconds to activate
impurities.
Japanese Patent Application Laid-Open No. 2008-004694 discloses the
technique of modifying a surface of a GaN substrate by the use of
an ultrashort pulsed laser such as a femtosecond laser. More
specifically, Japanese Patent Application Laid-Open No. 2008-004694
discloses the technique of irradiating the surface of the GaN
substrate with the pulsed laser to form an irregular structure, to
form an amorphous region or a strain region and to relax a
strain.
Japanese Patent Application Laid-Open No. 2014-078660 discloses the
technique of heating a region implanted with impurity ions in a
wide-gap semiconductor by laser annealing to activate the impurity
ions.
Unfortunately, it has been necessary for the conventional
techniques to repeatedly perform a modification process and the
inspection of a modification state in alternate order to set
conditions for light irradiation for the purpose of performing the
modification process under preferable conditions. Thus, complicated
operations and time-consuming feedback have been required for the
optimization of the conditions for light irradiation.
SUMMARY OF THE INVENTION
The present invention is intended for a modification processing
device for modifying a film by irradiating a semiconductor
substrate with light.
According to the present invention, the modification processing
device comprises: a light irradiation part for irradiating a
semiconductor substrate with light; and an electromagnetic wave
detection part for detecting the intensity of an electromagnetic
wave including a millimeter wave or a terahertz wave radiated from
the semiconductor substrate in response to the irradiation with
light.
The modification processing device is capable of detecting a change
in physical properties of the semiconductor substrate which results
from modification by detecting the millimeter wave or the terahertz
wave generated by the generation, disappearance and movement of
photocarriers. Therefore, the modification processing device is
capable of easily inspecting the modification state of the film in
the semiconductor substrate while performing the modification
process.
Preferably, the modification processing device further comprises a
modification determination part for determining the modification
state of a film of the semiconductor substrate, based on the
intensity of the electromagnetic wave detected by the
electromagnetic wave detection part.
The modification processing device is capable of easily inspecting
the modification state by determining the modification state.
Preferably, the modification processing device further comprises a
PL light detection part for detecting photoluminescent light
radiated from a surface of the semiconductor substrate by the
irradiation with light from the light irradiation part, wherein the
modification determination part determines the modification of the
semiconductor substrate, based on the intensity of the
electromagnetic wave detected by the electromagnetic wave detection
part and the photoluminescent light detected by the PL light
detection part.
The modification processing device is capable of inspecting the
modification state in further detail by detecting the
photoluminescent light.
Preferably, the modification processing device further comprises an
irradiation control part for controlling the irradiation with light
for modifying the film of the semiconductor substrate, based on a
result of determination of the modification determination part.
The modification processing device is capable of preferably
controlling the irradiation with light for modification in
accordance with the modification state.
Preferably, the light emitted from the light irradiation part is
pulsed light which modifies the film of the semiconductor substrate
and which generates an electromagnetic wave in the semiconductor
substrate.
This simplifies the device configuration because the same pulsed
light is used for the modification of the film and the generation
of the electromagnetic wave.
The present invention is also intended for a modification
monitoring device for monitoring the modification state of a film
in a semiconductor substrate.
According to the present invention, the modification monitoring
device comprises an electromagnetic wave detection part for
detecting an electromagnetic wave including a millimeter wave or a
terahertz wave radiated from said semiconductor substrate in
response to a irradiation with light.
The modification monitoring device is capable of inspecting the
modification state of the film in the semiconductor substrate,
based on the intensity of the millimeter wave or the terahertz
wave.
The present invention is also intended for a method of modifying a
film by irradiating a semiconductor substrate with light.
According to the present invention, the method comprises the steps
of: (a) irradiating a semiconductor substrate with light for
modifying a film; and (b) detecting the intensity of an
electromagnetic wave including a millimeter wave or a terahertz
wave radiated from the semiconductor substrate in response to the
irradiation with light in the step (a).
It is therefore an object of the present invention to provide a
technique for easily inspecting the modification state of a film of
a semiconductor substrate.
These and other objects, features, aspects and advantages of the
present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of a modification processing
device according to a first preferred embodiment of the present
invention;
FIG. 2 is a schematic sectional view showing a SiC Schottky barrier
diode formed in a semiconductor substrate;
FIG. 3 is a schematic plan view showing the SiC Schottky barrier
diode;
FIG. 4 is a schematic block diagram of a light irradiation part and
an electromagnetic wave detection part according to the first
preferred embodiment;
FIG. 5 is a schematic view showing a band structure of the
semiconductor substrate;
FIG. 6 is a graph showing an example of the time wave form of an
electromagnetic wave pulse;
FIG. 7 is a graph showing an example of a spectral distribution of
the electromagnetic wave pulse;
FIG. 8 is a flow diagram for illustrating a modification process
performed by the modification processing device according to the
first preferred embodiment;
FIG. 9 is a schematic block diagram of the modification processing
device according to a second preferred embodiment of the present
invention; and
FIG. 10 is a schematic block diagram of the modification processing
device according to a third preferred embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments according to the present invention will now
be described with reference to the accompanying drawings.
Components described in the preferred embodiments are merely
illustrative, and there is no intention to limit the scope of the
present invention thereto. In the drawings, the dimensions of
components and the number of components are shown in exaggeration
or in simplified form, as appropriate, for the sake of easier
understanding.
1. First Preferred Embodiment
<1.1. Configuration of Modification Processing Device 1>
FIG. 1 is a schematic block diagram of a modification processing
device 1 according to a first preferred embodiment of the present
invention. The modification processing device 1 is a device for
modifying a film in a semiconductor substrate 9 including a
semiconductor.
A semiconductor, as used herein, includes silicon (Si), germanium
(Ge), compound semiconductors such as gallium arsenide (GaAs), and
wide-gap semiconductors having a bandgap greater than that of Si,
such as gallium nitride (GaN) and silicon carbide (SiC). The first
preferred embodiment will be described on the assumption that a SiC
Schottky barrier diode is formed or is to be formed in the
semiconductor substrate 9.
FIG. 2 is a schematic sectional view showing a SiC Schottky barrier
diode 91 formed in the semiconductor substrate 9. FIG. 3 is a
schematic plan view showing the SiC Schottky barrier diode 91. In
the SiC Schottky barrier diode 91, an n-type SiC drift layer 93
serving as a withstand voltage layer for holding a withstand
voltage is provided by epitaxial growth on an n-type semiconductor
substrate 92 including an n-type low-resistance impurity such as N
(nitrogen) and P (phosphorus).
A p-type region 94 is formed in an upper part of the drift layer 93
by doping with a p-type impurity such as B (boron) and Al
(aluminum). The p-type region 94 is formed by implanting p-type
impurity ions from over the drift layer 93 and thereafter
performing a heat treatment (annealing process) step for activation
of the impurity ions. The modification processing device 1 is
configured to be capable of performing the aforementioned annealing
process for the formation of the p-type region 94.
An anode electrode 95 is provided on the drift layer 93. A cathode
electrode 96 is provided under the semiconductor substrate 92. The
anode electrode 95 serves as a Schottky electrode for the drift
layer 93. The p-type region 94 are positioned in a peripheral edge
part of the anode electrode 95, and serves as a guard ring region
provided for the purpose of preventing electric field concentration
in the vicinity of the peripheral edge part of the anode electrode
95. A region of an upper surface of the drift layer 93 where the
p-type region 94 is not formed functions as a Schottky barrier
diode.
Referring again to FIG. 1, the modification processing device 1
includes a stage 11, a light irradiation part 12, an
electromagnetic wave detection part 13, a photoluminescent light
(referred to hereinafter as "PL light") detection part 14, a stage
moving mechanism 15, a controller 16, a monitor 17 and an operation
input part 18.
The stage 11 holds the semiconductor substrate 9 on the stage 11 by
the use of a required fixing element. Conceivable examples of the
fixing element include holding tools for holding the semiconductor
substrate 9 therebetween, an adhesive sheet for affixing the
semiconductor substrate 9 thereto to fix the semiconductor
substrate 9, and a suction hole for fixing the semiconductor
substrate 9 by suction. Of course, other fixing elements capable of
fixing the semiconductor substrate 9 may be used.
FIG. 4 is a schematic block diagram of the light irradiation part
12 and the electromagnetic wave detection part 13 according to the
first preferred embodiment. The light irradiation part 12 includes
a pulse laser 121. The pulse laser 121 preferably emits laser light
(pulsed light LP1) having a pulse width of 1 femtosecond to 10
picoseconds.
The beam of pulsed light LP1 emitted from the pulse laser 121 is
split into two beams of pulsed light by a beam splitter B1. One of
the two beams of pulsed light is pulsed light LP11 which passes
through an optical system such as a lens to impinge on the
semiconductor substrate 9. Thus, the annealing process is
performed.
In the example shown in FIG. 1 or 4, the semiconductor substrate 9
is irradiated with the pulsed light LP11 so that the optical axis
of the pulsed light LP11 is incident obliquely on a main surface of
the semiconductor substrate 9. More specifically, the irradiation
angle of the pulsed light LP11 is set so that the incident angle
thereof is 45 degrees. The incident angle of the pulsed light LP11,
however, is not limited to such an angle but may be varied within a
range of 0 to 90 degrees, as appropriate. The pulsed light LP11
need not necessarily impinge upon the front surface of the
semiconductor substrate 9 but may impinge on a side surface or the
back surface of the semiconductor substrate 9.
As shown in FIG. 2 or 3, the irradiation of the p-type region 94,
that is, the front surface of the SiC Schottky barrier diode 91
with the pulsed light LP11 with the intention of performing the
annealing process generates an electromagnetic wave pulse LT1.
Photocarriers (free electrons and holes) generated by the
irradiation of the p-type region 94 of the SiC Schottky barrier
diode 91 with the pulsed light LP11 are accelerated by a depletion
layer of a pn junction and an internal electric field present at a
Schottky junction, so that a photoelectric current is generated and
disappears instantaneously. According to Maxwell's equations, when
a change occurs in current, an electromagnetic wave having an
intensity proportional to the time derivative of the current is
generated. The electromagnetic wave pulse LT1 generated from the
p-type region 94 includes a millimeter wave (30 to 300 GHz) or a
terahertz wave (0.1 to 30 THz). The generated electromagnetic wave
pulse LT1 is detected by the electromagnetic wave detection part 13
to be described later in detail.
The other of the two beams of pulsed light produced by the beam
splitter B1 is detection pulsed light LP12 which passes via a delay
part 131, mirrors and the like, and enters a detector 132. The
electromagnetic wave pulse LT1 generated in response to the
irradiation with the pulsed light LP11 is concentrated by a
parabolic mirror (not shown), passes via a mirror and the like, and
enters the detector 132.
The detector 132 serves as an electromagnetic wave detection
element including, for example, a photoconductive switch. It is
assumed that the detection pulsed light LP12 enters the detector
132 at the instant when the electromagnetic wave pulse LT1 enters
the detector 132. Then, a current in accordance with the electric
field strength of the electromagnetic wave pulse LT1 is generated
instantaneously in the photoconductive switch. The current in
accordance with the electric field strength is converted through an
I/V conversion circuit, an A/D conversion circuit and the like into
a digital quantity. In this manner, the electromagnetic wave
detection part 13 detects the electric field strength of the
electromagnetic wave pulse LT1 generated in the semiconductor
substrate 9 in response to the irradiation with the detection
pulsed light LP12. Other elements, e.g. an element to which a
non-linear optical crystal is applied, may be used for the detector
132.
The delay part 131 includes a delay stage 131a and a delay stage
moving mechanism 131b. The delay part 131 is an optical element for
continuously changing the time of arrival of the detection pulsed
light LP12 from the beam splitter B1 at the detector 132. The delay
stage 131a is linearly moved in the incident direction of the
detection pulsed light LP12 by the delay stage moving mechanism
131b. The delay stage 131a includes a reflecting mirror 10M for
reflecting the detection pulsed light LP12 back in the incident
direction.
More specifically, the delay stage moving mechanism 131b drives the
delay stage 131a, based on the control of the controller 16. Then,
the delay stage 131a moves linearly in the incident direction of
the detection pulsed light LP12, and the reflecting mirror 10M
accordingly moves linearly. Thus, the optical path length of the
detection pulsed light LP12 is precisely changed.
The delay stage 131a changes a time difference between the instant
at which the electromagnetic wave pulse LT1 arrives at the
electromagnetic wave detection part 13 (detector 132) and the
instant at which the detection pulsed light LP12 arrives at the
electromagnetic wave detection part 13 (detector 132). Thus, the
delay stage 131a changes the optical path length of the detection
pulsed light LP12 to thereby delay the time (detection time,
sampling time, or phase) at which the electric field strength of
the electromagnetic wave pulse LT1 is detected by the
electromagnetic wave detection part 13 (detector 132).
Other techniques may be used to change the time of arrival of the
detection pulsed light LP12 at the detector 132. Specifically, an
electro-optical effect may be used. That is, an electro-optical
element with a refractive index changed by changing the voltage
applied thereto may be used as a delay element. Specifically, an
electro-optical element disclosed in Japanese Patent Application
Laid-Open No. 2009-175127 may be used.
Alternatively, a delay part for changing the optical path length of
the pulsed light LP11 or the optical path length of the
electromagnetic wave pulse LT1 radiated from the semiconductor
substrate 9 may be provided. In this case, the instant at which the
electromagnetic wave pulse LT1 arrives at the detector 132 may be
shifted relative to the instant at which the detection pulsed light
LP12 arrives at the detector 132. This delays the time at which the
electric field strength of the electromagnetic wave pulse LT1 is
detected by the detector 132.
The PL light detection part 14 includes a spectroscope 141 and a
light detector 143. The light detector 143 is formed by a
photodiode. The recombination of the photocarriers generated in the
SiC Schottky barrier diode 91 due to irradiation with the pulsed
light LP11 generates PL light PL1. The PL light detection part 14
detects the generated PL light PL1.
FIG. 5 is a schematic view of a band structure of the semiconductor
substrate 9. For the annealing process, the pulsed light LP11
having energy E1 exceeding the excitation level is emitted from the
ground level which is the energy gap of the semiconductor (in this
case, SiC) constituting the semiconductor substrate 9, as shown in
FIG. 5. Thus, heat and the PL light PL1 are generated when the
excited photocarriers make a transition to the ground level. The
p-type region 94 is annealed by the generated heat.
A relation between bandgap energy Eg and the wavelength .lamda.
(nm) of light is expressed as ".lamda.=hc/Eg". For example, the
bandgap of 4H-SiC is 3.26 eV. The wavelength absorbed by this
semiconductor is less than 380 nm.
As shown in the right-hand part of FIG. 5, the annealing process by
the use of the pulsed light LP11 having a wavelength which is
energy E2 lower than the energy E1 exceeding the forbidden band may
be performed by using a trap level resulting from impurities and
defects. That is, it is only necessary that the energy of light is
converted into heat, and the pulsed light LP11 for modification
need not necessarily have the wavelength of the energy equal to or
greater than the bandgap.
The amount of heat generated is dependent on the intensity (the
number of photons) of the pulsed light LP1. Decrease in the
intensity of the pulsed light LP1 for irradiation allows the
generation of the electromagnetic wave pulse LT1 and the PL light
while preventing the annealing from proceeding. This achieves the
inspection of the modification state of the film of the
semiconductor substrate 9, based on the electromagnetic wave pulse
LT1 or the PL light PL1.
Referring again to FIG. 1, the stage moving mechanism 15 includes
an X-Y table for moving the stage 11 in a two-dimensional plane.
The stage moving mechanism 15 drives the X-Y table to move the
semiconductor substrate 9 held on the stage 11 relative to the
light irradiation part 12. Thus, by the provision of the stage
moving mechanism 15, the modification processing device 1 is
capable of moving the semiconductor substrate 9 to any position in
the two-dimensional plane. This allows the pulsed light LP11 to
scan a region (to-be-annealed region) required to be annealed in
the semiconductor substrate 9, for example. Also, the stage 11 may
be moved manually, with the driving source of the stage moving
mechanism 15 dispensed with.
The stage moving mechanism 15 is an example of a scanning
mechanism. For example, a moving element for moving the light
irradiation part 12 in a two-dimensional plane may be provided in
place of or in addition to moving the semiconductor substrate 9. In
either case, the irradiation of the to-be-annealed region in the
semiconductor substrate 9 with the pulsed light LP11 is achieved.
It is also contemplated that a region to be inspected is scanned by
the pulsed light LP11 by changing the optical path of the pulsed
light LP11. Specifically, it is contemplated that a galvanometer
mirror is provided to cause the pulsed light LP11 to scan in two
directions parallel to the surface of the semiconductor substrate 9
and orthogonal to each other. It is also contemplated that a
polygon mirror, a piezoelectric mirror, an acousto-optical element
or the like is used in place of the galvanometer mirror.
The controller 16 is configured as a typical computer including a
CPU, a ROM, a RAM and an auxiliary storage part (for example, a
hard disk). The controller 16 is connected to the pulse laser 121
of the light irradiation part 12, the delay stage 131a and the
detector 132 of the electromagnetic wave detection part 13, the PL
light detection part 14 and the stage moving mechanism 15. The
controller 16 controls the operations of these components and
receives data from these components.
More specifically, the controller 16 receives data about the
electric field strength of the electromagnetic wave pulse LT1 from
the detector 132, for example. The controller 16 also controls the
delay stage moving mechanism 131b for moving the delay stage 131a.
Further, the controller 16 receives data about the position of the
delay stage 131a, such as a distance of movement of the reflecting
mirror 10M, from a linear scale provided in the delay stage 131a
and the like.
The controller 16 includes an image generation part 21, a time wave
form restoration part 22, a spectral analysis part 23, a
spectroscopic data analysis part 24, a modification determination
part 25, an irradiation control part 26 and an irradiation area
specification part 27. These parts may be functions implemented by
the CPU in the controller 16 operating in accordance with programs
or be formed by purpose-built circuits in the form of hardware.
The image generation part 21 generates an electric field strength
distribution image which presents a distribution of the electric
field strength of the electromagnetic wave pulse LT1 generated from
the semiconductor substrate 9 in visual form. In this electric
field strength distribution image, differences in electric field
strength are represented visually using different colors, shades of
color or different patterns.
The time wave form restoration part 22 restores the time wave form
of the electromagnetic wave pulse LT1, based on the electric field
strength of the electromagnetic wave pulse LT1 detected by the
electromagnetic wave detection part 13 (detector 132).
Specifically, the time wave form restoration part 22 moves the
reflecting mirror 10M of the delay stage 131a to change the optical
path length (optical path length of a first optical path) of the
detection pulsed light LP12, thereby changing the time of arrival
of the detection pulsed light LP12 at the detector 132. This
changes the time (phase) at which the detector 132 detects the
electric field strength of the electromagnetic wave pulse LT1. The
time wave form restoration part 22 detects the electric field
strength of the electromagnetic wave pulse LT1 for each phase. The
detected electric field strengths are plotted along the time axis.
Thus, the time wave form restoration part 22 restores the time wave
form of the electromagnetic wave pulse LT1.
The spectral analysis part 23 performs a spectral analysis on the
restored electromagnetic wave pulse LT1. Specifically, the spectral
analysis part 23 performs Fourier transformation on the time wave
form restored by the time wave form restoration part 22 to acquire
an amplitude intensity spectrum for each frequency.
FIG. 6 is a graph showing an example of a time wave form 41 of the
electromagnetic wave pulse LT1. FIG. 7 is a graph showing an
example of a spectral distribution 51 of the electromagnetic wave
pulse LT1. The spectral distribution 51 shown in FIG. 7 is obtained
by performing Fourier transformation on the time wave form 41 shown
in FIG. 6. For example, the analysis of the spectral distributions
of the electromagnetic wave pulse LT1 generated from the
semiconductor substrate 9 before and after the annealing process of
the semiconductor substrate 9 provides the more detailed analysis
of changes in electric field strength of the electromagnetic wave
pulse LT1 which the modification state provided by the annealing
process is reflected.
The spectroscopic data analysis part 24 analyzes the PL light PL1
detected by the PL light detection part 14. Specifically, the
spectroscopic data analysis part 24 acquires the intensity
(wavelength profile) for each wavelength of the PL light PL1
detected by the PL light detection part 14. The acquisition of the
wavelength profile of the PL light PL1 achieves the analysis of the
modification state provided by the annealing process. As the
annealing process proceeds, the intensity or wavelength of the
generated PL light PL1 is changed. Thus, the modification state of
the film is suitably seized by monitoring the intensity or
wavelength of the PL light PL1.
The modification determination part 25 determines whether the
modification of the film of the semiconductor substrate 9, i.e. the
annealing process, is completed or not, based on the intensity of
the electromagnetic wave pulse LT1 detected by the detector
132.
After the film is modified by the annealing process, the
intensities of the electromagnetic wave pulse LT1 and the PL light
PL1 generated are changed. For example, the modification of the
p-type region 94 changes the characteristics of a p-n junction or a
p-metal junction. This changes the intensity of the generated
electromagnetic wave pulse LT1. That is, the modification state is
suitably seized by monitoring the intensity of the electromagnetic
wave pulse LT1 while performing the annealing process.
The modification state of the film irradiated with the pulsed light
LP11 is monitored by the provision of the electromagnetic wave
detection part 13. Thus, the electromagnetic wave detection part 13
may be interpreted as a modification monitoring device. A
combination of the modification determination part 25, the PL light
detection part 14 and the spectroscopic data analysis part 24 in
addition to the electromagnetic wave detection part 13 may be
interpreted as a modification monitoring device.
In the present preferred embodiment, the modification determination
part 25 determines whether the annealing process is completed or
not, based on the intensity of the electromagnetic wave pulse LT1
generated from the semiconductor substrate 9 during the annealing
process. A conceivable example of this determination method
includes making a comparison between the intensity of the detected
electromagnetic wave pulse LT1 and a predetermined threshold value
of the intensity of the electromagnetic wave pulse LT1 assumed that
the annealing process is completed.
The modification determination part 25 also determines the
modification of the semiconductor substrate 9, based on the PL
light PL1 detected by the PL light detection part 14. More
specifically, the modification determination part 25 monitors the
intensity or wavelength of the PL light PL1 acquired by the
spectroscopic data analysis part 24 during the annealing process.
It can be considered that the modification determination part 25
determines that the annealing process is completed when the
intensity or wavelength of the PL light PL1 is changed to that
obtained after the modification.
The irradiation control part 26 controls the irradiation of the
semiconductor substrate 9 with the pulsed light LP11, based on the
result of determination of the modification determination part 25.
Specifically, for example, when the modification determination part
25 determines that the annealing process of a region irradiated
with the pulsed light LP11 is completed, the irradiation control
part 26 stops the irradiation of the region with the pulsed light
LP11. A conceivable example of the method of stopping the
irradiation with the pulsed light LP11 includes stopping the
emission of light from the light irradiation part 12 by
intercepting light on the optical path of the pulsed light LP1 or
the pulsed light LP11. Another conceivable example of the method
includes moving the semiconductor substrate 9 to change the
irradiation position of the pulsed light LP11 to a different
position. In this manner, the irradiation control part 26 is
capable of completing the annealing process at a preferable time by
stopping the irradiation with the pulsed light LP11, based on the
result of determination of the modification determination part
25.
Alternatively, the irradiation control part 26 may control the
amount of light per unit area so as to increase or decrease, for
example, without completely stopping the irradiation with the
pulsed light LP11. Specifically, the irradiation control part 26
may control the light irradiation part 12 so as to increase or
decrease the amount of light per unit area of the pulsed light LP11
when the intensity of the electromagnetic wave pulse LT1 is higher
or lower than a predefined threshold value.
Also, the irradiation control part 26 may control the light
irradiation part 12 so as to stop the irradiation with the pulsed
light LP11 or to increase or decrease the amount of light per unit
area, based on the intensity or wavelength of the PL light PL1.
The irradiation area specification part 27 specifies an area of the
film to be modified. More specifically, for the annealing process
of the semiconductor substrate 9, the irradiation area
specification part 27 specifies the position of the anode electrode
95 serving as an interconnect line portion in the semiconductor
substrate 9 from a circuit diagram. Then, the irradiation area
specification part 27 specifies an area around the anode electrode
95 as an irradiation area to be irradiated with the pulsed light
LP11 for the purpose of forming the p-type region 94. The
irradiation control part 26 irradiates the irradiation area
specified by the irradiation area specification part 27 with the
pulsed light LP11.
<1.2. Modification Process>
FIG. 8 is a flow diagram for illustrating the modification process
performed by the modification processing device 1 according to the
first preferred embodiment. The operations of the modification
processing device 1 are performed under the control of the
controller 16, unless otherwise specified.
First, the step of preparing the semiconductor substrate 9 is
performed (Step S1). In this step, the semiconductor substrate 9 is
transported onto the stage 11, and is held on the stage 11. Then,
alignment is performed, as appropriate.
After the preparation of the semiconductor substrate 9 is
completed, the irradiation area to be irradiated with the pulsed
light LP11 is specified (Step S2). Specifically, the position in
which the p-type region 94 is to be formed is specified by
specifying the position of the interconnect line portion from a
circuit diagram represented by CAD data and the like. This
specified position is defined as the irradiation area.
After the specification of the irradiation area is completed, the
annealing process is performed (Step S3). Specifically, the
semiconductor substrate 9 is moved so that the specified
irradiation area coincides with the irradiation position of the
pulsed light LP11. The annealing process is performed by
irradiation with the pulsed light LP11. While the annealing process
is being performed, the detection of the electromagnetic wave pulse
LT1 generated from the semiconductor substrate 9 by the irradiation
with the pulsed light LP11 and the detection of the PL light PL1
are performed.
As mentioned above, the irradiation with the pulsed light LP11 is
performed based on the control of the irradiation control part 26.
Specifically, when the annealing process at a specific location
proceeds, the modification determination part 25 determines whether
the modification is made or not, based on the intensity of the
electromagnetic wave pulse LT1 and the intensity or wavelength
profile of the PL light PL1. When the modification determination
part 25 determines that the modification is completed, the
irradiation control part 26 changes the irradiation position of the
pulsed light LP11 or stops the emission of light from the light
irradiation part 12 to thereby stop the irradiation with the pulsed
light LP11. The annealing process is performed in this manner.
After the annealing process is completed, the modification
processing device 1 scans the semiconductor substrate 9 with the
pulsed light LP11 for the purpose of inspecting the semiconductor
substrate 9 (Step S4). In Step S4, the range to be scanned is
arbitrarily determined, but the region subjected to the annealing
process in Step S3 by the pulsed light LP11, for example, is
scanned. Then, information about the intensity of the
electromagnetic wave pulse LT1 generated is collected.
For the collection of the information about the electromagnetic
wave pulse intensity, the intensity of the electromagnetic wave
pulse LT1 at a single certain detection time (phase) may be
detected while the delay stage 131a is fixed. Alternatively, the
intensity of the electromagnetic wave pulse LT1 may be detected at
a plurality of detection times. For the detection of the intensity
at the plurality of detection times, the same region may be scanned
a plurality of times at respective different detection times.
Alternatively, the electromagnetic wave pulse LT1 may be measured
at the plurality of detection times by irradiation with the pulsed
light LP11 while the delay stage 131a is moved to predefined
positions at each inspection points of the region during the single
scanning of the region.
After the scanning in Step S4 is completed, the modification
processing device 1 generates and displays an image (Step S5).
Specifically, the image generation part 21 generates an
electromagnetic wave intensity distribution image, based on
electromagnetic wave intensity data collected in Step S4. The
generated image is displayed on the monitor 17.
The generation and display of the electromagnetic wave intensity
distribution image as in Step S4 and Step S5 allows the
semiconductor substrate 9 after the annealing process to be
inspected for various defects (inclusion of impurities, cracks,
electrode formation failures and the like). It should be noted that
Steps S4 and S5 may be dispensed with. Also, a region of the
semiconductor substrate 9 other than the region subjected to the
annealing process may be inspected in Steps S4 and S5.
The time wave form (with reference to FIG. 6) of the
electromagnetic wave pulse LT1 may be restored at any time before,
during and after the annealing process. The frequency analysis of
the electromagnetic wave pulse LT1 may be performed by doing
Fourier transformation on the restored time wave form.
As described above, the electromagnetic wave pulse LT1 is detected
in the modification processing device 1 while the annealing process
is performed. The detection of the electromagnetic wave pulse LT1
allows the quantitative measurements of the generation,
recombination and movement of photocarriers or changes in the
electrical conductivity of an electrically conductive film. Thus,
the modification state of the semiconductor substrate 9 provided by
the annealing process is suitably monitored by monitoring these
parameters.
Also, the PL light PL1 is detected in the modification processing
device 1 while the annealing process is performed. The PL light PL1
is light emitted when excited electrons and holes are recombined
together. That is, the measurement of the PL light PL1 allows the
quantitative analysis of the characteristics of the semiconductor
substrate 9 such as band-to-band recombination, recombination
between a band and a trap level and recombination between trap
levels. Thus, the modification state of the semiconductor substrate
9 provided by the annealing process is suitably seized.
As mentioned above, the modification processing device 1 is capable
of monitoring the intensity of the electromagnetic wave pulse LT1
and the intensity or wavelength of the PL light PL1. This allows
the inspection of the modification state of the film, so that the
annealing process is performed under preferable conditions. Also,
the modification processing device 1 is capable of inspecting the
modification state in a non-contacting manner. Thus, the
semiconductor substrate 9 need not be transported to the outside
for the inspection. This reduces the danger of damages to the
semiconductor substrate 9 to achieve the inspection of the
modification state easily.
2. Second Preferred Embodiment
Next, a second preferred embodiment according to the present
invention will be described. In the following description,
components having the same functions as those described above are
designated by like reference numerals and characters or like
reference numerals and characters with alphabetic characters
appended thereto, and will not be described in detail in some
cases.
FIG. 9 is a schematic block diagram of a modification processing
device 1A according to the second preferred embodiment. In the
modification processing device 1A, the pulsed light LP11 passes
through a hole formed in a parabolic mirror M1 and impinges
perpendicularly on the main surface of the semiconductor substrate
9. Thus, the annealing process for the formation of the p-type
region 94 is performed locally. The electromagnetic wave pulse LT1
generated in response to the irradiation with the pulsed light LP11
and emitted on the main surface side irradiated with the pulsed
light LP11 is concentrated by parabolic mirrors M1 and M2 and
detected by the detector 132. Part of the PL light PL1 generated in
response to the irradiation with the pulsed light LP11 and radiated
in a direction coaxial with the optical axis of the pulsed light
LP11 passes through the hole in the parabolic mirror M1, is
reflected from a half mirror M3, enters the spectroscope 141, and
is detected by the light detector 143.
Like the modification processing device 1 of the first preferred
embodiment, the modification processing device 1A is capable of
acquiring the intensity of the electromagnetic wave pulse LT1 and
the intensity or wavelength of the PL light PL1 during the
annealing process. This allows the inspection of the modification
state of the film, so that the annealing process is performed under
preferable conditions. Also, the modification processing device 1A
is capable of inspecting the modification state in a non-contacting
manner. Thus, the semiconductor substrate 9 need not be transported
to the outside for the inspection. This reduces the danger of
damages to the semiconductor substrate 9 to achieve the inspection
of the modification state easily.
3. Third Preferred Embodiment
FIG. 10 is a schematic block diagram of a modification processing
device 1B according to a third preferred embodiment of the present
invention. In the modification processing device 1B, the pulsed
light LP11 impinges perpendicularly on the main surface of the
semiconductor substrate 9. Thus, the annealing process for the
formation of the p-type region 94 is performed locally. Part of the
electromagnetic wave pulse LT1 generated in response to the
irradiation with the pulsed light LP11 and transmitted through the
semiconductor substrate 9 toward the back surface side of the
semiconductor substrate 9 is concentrated by parabolic mirrors M4
and M5 and detected by the detector 132. Part of the PL light PL1
generated in response to the irradiation with the pulsed light LP11
and radiated in a direction coaxial with the optical axis of the
pulsed light LP11 is reflected from the half mirror M3, enters the
spectroscope 141, and is detected by the light detector 143.
Like the modification processing device 1 of the first preferred
embodiment, the modification processing device 1B is capable of
monitoring the intensity of the electromagnetic wave pulse LT1 and
the intensity or wavelength of the PL light PL1 during the
annealing process. This allows the inspection of the modification
state of the film, so that the annealing process is performed under
preferable conditions. Also, the modification processing device 1B
is capable of inspecting the modification state in a non-contacting
manner. Thus, the semiconductor substrate 9 need not be transported
to the outside for the inspection. This reduces the danger of
damages to the semiconductor substrate 9 to achieve the inspection
of the modification state easily.
4. Modifications
In the modification processing device 1, the light irradiation part
12 irradiates the semiconductor substrate 9 with the pulsed light
LP11 for the annealing process. However, the light irradiation part
12 may irradiate the semiconductor substrate 9 with other types of
light.
For example, the light irradiation part 12 may be designed to
perform flash lamp annealing. In this case, the light irradiation
part 12 irradiates the semiconductor substrate 9 with a flash of
light, and irradiates the semiconductor substrate 9 with the pulsed
light LP11 separately. This achieves the generation of the
electromagnetic wave pulse LT1 and the PL light PL1 while
performing the annealing process.
Two light sources which emit two beams of continuous light slightly
different in oscillation frequency from each other may be used in
place of the pulse laser 121 to generate an electromagnetic wave
(as disclosed in Japanese Patent Application Laid-Open No.
2013-170864). Specifically, the two beams of continuous light are
superimposed by means of a coupler formed by an optical fiber such
as an optical waveguide to generate an optical beat signal
corresponding to the difference frequency. This optical beat signal
is caused to impinge on the semiconductor substrate 9, so that an
electromagnetic wave corresponding to the frequency of the optical
beat signal is radiated.
The modification processing device 1 may include a spectroscope and
a light detector for detecting Raman scattered light. The Raman
scattered light includes various pieces of information about the
molecular state of the semiconductor substrate 9. Thus, the
modification state provided by the annealing process is inspected
by analyzing the Raman scattered light.
In the preferred embodiments, the annealing process in the field of
semiconductor manufacture is described as the process for modifying
the film in the semiconductor substrate 9. The process for
modifying the film is not limited to the annealing process, but
includes other processes. For example, a surface treatment for
forming an uneven structure resulting from ablation on a surface,
and a process for crystallizing an amorphous material are included
in the modification process.
Further, the modification processing device 1 may use other types
of semiconductor devices or semiconductor wafers as the
semiconductor substrate. The modification processing device 1 may
process a semiconductor substrate having no electrodes formed
thereon.
While the invention has been described in detail, the foregoing
description is in all aspects illustrative and not restrictive. It
is understood that numerous other modifications and variations can
be devised without departing from the scope of the invention.
* * * * *